Organismal and Evolutionary Biology, University of Helsinki, Helsinki, Finland.
Glob Chang Biol. 2022 Nov;28(22):6577-6585. doi: 10.1111/gcb.16381. Epub 2022 Aug 19.
The frequency and duration of heatwaves are increasing because of human activities. To cope with the changes, species with longer generation times may have to rely on plastic responses. The probability that their responses are adaptive is higher if the species have experienced temperature fluctuations also in their evolutionary past. However, experimental studies investigating responses to heatwaves often use exposure times that are significantly shorter than recent heatwaves. We show that this can lead to faulty conclusions and that the duration of higher temperature has to be considered in experimental designs. We recorded the response of threespine stickleback to prolonged duration of higher temperature during the breeding season, using a population that has experienced large fluctuations in temperature in its past and, hence, is expected to endure temperature changes well. We found males to adaptively adjust their reproductive behaviours to short periods of higher temperature, but not to longer periods that extended across two breeding cycles. Males initially increased their reproductive activities-nest building, courtship and parental care-which ensured high reproductive success during the first breeding cycle, but decreased their reproductive activities during the second breeding cycle when exposed to sustained high temperature. This reduced their courtship success and resulted in fewer offspring. Thus, a species expected to cope well with higher temperature suffers fitness reductions when the duration of high temperature is prolonged. The results stress the importance of considering the duration of extreme environmental conditions when investigating the impact that human activities have on species. Responses to short-term exposures cannot be extrapolated to assess responses to longer periods of extreme conditions.
由于人类活动的影响，热浪的频率和持续时间正在增加。为了应对这些变化，世代时间较长的物种可能不得不依赖于可塑性反应。如果这些物种在进化过程中也经历过温度波动，那么它们的反应具有适应性的可能性就更高。然而，研究对热浪的反应的实验研究通常使用的暴露时间明显短于最近的热浪。我们表明，这可能导致错误的结论，并且必须在实验设计中考虑到较高温度的持续时间。我们记录了三刺鱼在繁殖季节对较长时间的较高温度的反应，使用的种群在过去经历了较大的温度波动，因此预计能够很好地耐受温度变化。我们发现，雄性会自适应地调整其繁殖行为以适应短期的高温，但不会适应跨越两个繁殖周期的较长时间的高温。雄性最初会增加其繁殖活动——筑巢、求偶和育雏——以确保在第一个繁殖周期中获得高繁殖成功率，但在暴露于持续高温时，它们会在第二个繁殖周期中减少繁殖活动。这降低了它们的求偶成功率，导致后代数量减少。因此，一个预计能够很好地应对高温的物种，当高温持续时间延长时，其适应能力会降低。这些结果强调了在研究人类活动对物种的影响时，考虑极端环境条件持续时间的重要性。不能将短期暴露的反应推断为评估更长时间极端条件下的反应。
